This invention relates to carburetors provided with an electric heating type autochoke device.
In this type of autochoke device, it has previously been known to use a resistance element of positive temperature coefficient in order to detect any overheat state of the bimetal chamber and prevent the bimetal element from being excessively heated.
To serve this purpose, a definite correlation is required between the thermal deformation characteristic of the bimetal element under the effect of the electric heater means and the heater-current controlling characteristic of the resistance element, which is heated by the same electric heater means, and the relationship must be such that it is not until the bimetal is sufficiently deformed under heat to open the choke valve that the positive temperature coefficient resistance element acts to control the flow of heater current. Should the resistance element be heated enough to control the flow of heater current before the bimetal has been fully heated, the choke valve would not be fully opened owing to the insufficient deformation of the bimetal element. Contrariwise, if the amount of heat given to the resistance element be not enough to control the heater current even at the time when the bimetal element has been fully heated to open the choke valve, an excessive amount of thermal stress must develop in the bimetal. This has involved various problems such as deterioration of the bimetal and increase in electric power consumption, making it necessary to give special consideration to the location of the resistance element and its mounting relative to the heater means.